As a longtime SIBO sufferer and frequent rifaximin (and one time neomycin user), the strategy of "eating food to make the bacteria flourish so you can kill them more readily" makes sense. Both of these antibiotics have the potential to mess up your digestion to begin with but stick with it. I would recommend 2-4 days of "eating normally" (what you consider normal right now) to let the antibiotics do some damage, and then switch to eating more "conventionally" "normally", or even going out of your way to eat specific foods that feed the bacteria, for the rest of the treatment. Maybe you already know which foods set you off the most so you can go and get those, but in my case and in many others, the "gum" additives found in most "processed" foods are the best/worst (guar gum and xanthum gum being the most noteworthy, and then carob bean gum). The product "Tomorrow's Nutrition, Sunfiber, Prebiotic Fiber Supplement for Digestive Health" which you can find on Amazon is pure guar gum, if you don't want to raid the cookie/icecream aisle at your grocery store (or do both since it's the middle of summer).

Good luck, hope you get your Rx filled.